Various arrangements are known which couple a drive assembly such as a motor and specifically the motor shaft to a machine shaft which is used to drive various mechanisms, including mechanical devices, such as a pump or the wheels of a vehicle, referred to as a driven assembly.
Most of these coupling arrangements are completely mechanical, using various gear and clutch arrangements. Various control arrangements are used to assist in the efficient coupling of the drive assembly to the driven assembly, including both mechanical and electronic devices.
A primary disadvantage of mechanical coupling arrangements is that the mechanical parts tend to wear and eventually break; the mechanical arrangement can also be complex, in both the number and the type of parts required. Also, conventional systems are usually inefficient, because the motor does not run consistently at its most efficient speed; the driven assembly/machine must operate under varied conditions of torque as well as speed. The motor is controlled, with various gear ratios, to satisfy the varying requirements of the driven assembly.
One attempt to overcome the disadvantages of a purely mechanical coupling is a magnetic coupling arrangement between the motor (the drive member) and the driven member. An example of such a magnetic coupling using two discs in registry is shown in U.S. Pat. No. 5,668,424 to Lamb et al, as well as several other patents to Lamb. However, such magnetic coupling arrangements have their own disadvantages, in that rather complicated control mechanisms must be used to control the physical distance between the magnetic coupling elements. Further, the power capacity of such existing systems is increased only by increasing the diameter of the two discs, which has practical limitations in most systems.
A magnetic coupling system which would overcome the above disadvantages of existing magnetic coupling devices would be advantageous in many applications.